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Hybrid perovskite materials are promising for application as the active layers in solar cells due to their excellent optoelectronic properties. Improved understanding of the origins of hysteresis in perovskite materials must be established to overcome barriers to commercialization. In this study, we use a lateral device geometry to bias a methylammonium lead bromide thin film single crystal. Upon biasing, the halide concentration varies laterally within the crystal, as observed by means of nondestructive synchrotron-based nanoprobe X-ray fluorescence (Nano-XRF). The direct observation of a partially reversible bromine re-distribution under bias is revealed experimentally. The origins of device hysteresis and switchable effects can be partially explained by the local elemental information available from Nano-XRF.

Quasi-2D perovskite photovoltaics have been shown to have better stability than their 3D counterparts but the effects of the A-site cation on charge collection have not been fully clarified in these systems. In this study, the nanoscale carrier collection properties within quasi-2D bromide based lead perovskites (n=3 and 40) are found to be uncorrelated with local variations in halide stoichiometry, in contrast to the 3D perovskite. The local elemental distribution is quantified by means of synchrotron-based nanoprobe X-ray fluorescence (Nano-XRF), while the local carrier collection is simultaneous collected via X-ray beam induced current (XBIC).